The valves just seem to be a plain shutoff (no check valve).
The 3/8 barb can be replaced with a 1/4 barb, both of which must have the same threads per the micromatic web site replacement parts.
The valve in #31 does look slightly different though.
The 3/8 barb can be replaced with a 1/4 barb, both of which must have the same threads per the micromatic web site replacement parts.
The valve in #31 does look slightly different though.